Seasonal influenza vaccination strategies

The immunity that is elicited by influenza vaccines is not as long lived as the immunity following natural influenza infection. This is especially so for individuals in the so-called risk groups, hence people have to be vaccinated annually.

There are three possible influenza immunisation strategies but the first is the most important and widely used in Europe.

1. Protecting the vulnerable

The main strategy of immunisation programmes in Europe is to directly or indirectly protect the more vulnerable individuals. Direct protection involves immunising people who are more likely to develop severe disease if they are infected by influenza viruses (risk groups). In December 2009 the EU Council adopted a Council Recommendation on seasonal influenza vaccination. The Recommendation encourages the EU Member States to adopt and implement action plans and policies aimed at reaching seasonal influenza vaccination coverage among older age groups of 75%, and if possible that target be extended to people with chronic medical conditions. Member States are also encouraged to improve vaccination coverage among healthcare workers. ECDC has monitored progress towards the targets of the Council Recommendation drawing on data, analyses and actions undertaken in recent years presented in the technical report Implementation of the Council recommendation on seasonal influenza vaccination.

While immunising members of risk groups means direct protection, there is also an indirect protection strategy of immunising those with close contact with people in the risk groups. This is growing in importance since it is now appreciated that the routinely used influenza vaccines are more effective in healthy children and adults than older people and those with chronic conditions including immunodeficiency. Further, children under 6 months of age that cannot be vaccinated with current vaccines may be protected by the indirect protection strategies.

2. Protecting healthy children, adolescents and adults

Healthy toddlers and younger children are prone to severe influenza disease. A number of EU/EEA countries, including Finland, Latvia and United Kingdom have initiated immunisation programmes for these younger age groups.

Influenza epidemics are also an important cause of many bouts of short-lived but debilitating illness leading to school and work absence. Hence many people choose to get immunised and some also have their children immunised regardless of whether there is a formal recommendation or universal vaccination programme.

In addition, due to the economic impact and social disruption, employers often encourage immunisation of their staff and make it readily available. This includes employers of healthcare staff though the prime reason for immunising healthcare workers is protecting their patients.

3. Reducing overall influenza transmission

This is a new approach based on the observation that much of the influenza transmission takes place in children’s day care facilities and amongst school age children. So immunising children and adolescents in addition to the older population, may reduce overall influenza transmission and protect those in the risk groups. This is an approach recently adopted by the United Kingdom rolling out a programme offering influenza vaccine to all children 2-11 years of age.